News of Simm's return delighted fans when it was announced a few months ago following a leak – though given that he returns in disguise in the penultimate episode of series 10, it didn't come as a massive shock when the eventual reveal happened.

Many fans noted that had it not been known that The Master was back beforehand, it would have made the reveal a massive surprise.

Now Simm himself has weighed in on the matter, arguing that it was wrong to let the cat out of the bag so early.

"I'd never been given the opportunity to use prosthetics and sort of hide underneath this brilliant face that they gave me," he told Doctor Who Magazine of his disguise as Razor in 'World Enough and Time'. "That was just so good. I could really play with that.

"So I was a bit disappointed when they let it out that I was coming back. Because the audience is obviously going to guess that that's me, aren't they?"

"We're at this moment filming the Twelfth Doctor and the First Doctor meeting," Moffat said. "I can say right now I've just been on the set of the First Doctor's TARDIS, which has been beautifully created over there.

"David Bradley's creation of William Hartnell is so eerily perfect, it could fool you. I've just been watching a scene in the other studio where he is so perfectly William Hartnell, you could be convinced it's him."

Doctor Who Magazine issue 514 is on sale now. Watch our review of the Doctor Who series 10 finale 'The Doctor Falls' below: